This application is a United States National Phase application which claims priority on British Application No. GB 99 07877.6, filed Apr. 8, 1999 and British Application No. GB 00 03128.6, filed Feb. 14, 2000.
1. Technical Field
This invention relates to a device for training an operative, for example medical personnel and anaesthetic assistants, in the correct application and monitoring of force to the cricoid cartilage of a patient undergoing tracheal intubation, for example at the onset of anaesthesia. It can also be used as device for use directly on patients to apply said force.
2. Background Art
The application of cricoid force is an important technique, which is routinely used during emergency and obstetric anaesthesia. The technique involves the application of external force on the cricoid cartilage (at the front of the neck) to occlude the lumen of the oesophagus which lies behind it. The aim of the technique is to prevent the inhalation of regurgitated stomach contents into the lungs when the patient loses consciousness at the onset of anaesthesia. The inhalation of vomit should it occur is very serious as it causes severe inflammation of the lungs and the outcome may be fatal. Although the technique will be referred to hereinafter with reference to force (as in xe2x80x9capplied cricoid forcexe2x80x9d or ACF) it should be appreciated that the technique is also commonly referred to with reference to pressure (as in xe2x80x9capplied cricoid pressurexe2x80x9d or ACP). Thus, xe2x80x9cforcexe2x80x9d as used herein is to be interpreted as encompassing xe2x80x9cpressurexe2x80x9d and vice versa except where such an interpretation would be contrary to the contextual meaning.
Sellick first described the ACF technique, in 1961. It involves the use of three fingers; the index finger is used to apply pressure on the cricoid cartilage and the middle finger and the thumb to stabilise the larynx during the procedure. The force required is equal to 40 Newtons. The anaesthetist""s assistant during induction of anaesthesia should consistently maintain this force until the anaesthetist secures the patient airway by inserting a cuffed tracheal tube in the trachea (windpipe).
It is important that the exact force should be applied as the application of an excessive force on the cricoid cartilage distorts the larynx and makes tracheal intubation difficult. On the other hand, if the force is applied is inadequate, the patient may be subjected to the dangers of inhalation of stomach contents.
Several studies have shown that it is difficult to consistently apply the exact cricoid force and that there is wide individual variation in the ACF with 47%-61% of medical staff applying an inadequate force. It has also been shown that to apply the correct force, frequent training in the manoeuvre is required as retention of skills after acquiring the experience is short lived To gain experience, trainees practice on weight scales to be able to manually reproduce the correct ACF. It is also possible to train anaesthetic assistants to reproduce the correct force during simulated ACF but mechanical simulators are not readily available and are expensive. It is, therefore, necessary to provide a simple and readily available training tool to allow frequent training and to maintain skills. No training devices currently exist but a few devices for the application of the ACF directly on a patient are available. However, they have not been widely adopted in clinical practice. This is largely because of various shortcomings including complexity, expense, reliance on electricity/battery supply, delay in setting up the equipment when urgently required or they are heavy resulting in laryngeal distortion and difficult tracheal intubation. For these reasons, currently, manual application of cricoid pressure, with its aforesaid shortcomings, remains the predominant method.
It is one aim of the present invention to provide means for enabling ACF to be applied correctly, and consistently, for a sufficient period of time. It is a further aim of the present invention to provide means for training an operative in the ACF procedure.
It is yet a further aim of the present invention to provide means for both the application of cricoid force to a patient, and for training an operative to do so.
It is yet a further aim of the present invention to provide an ACF device and/or training device which addresses the problems of prior art devices of this type, whether referred to herein or otherwise.
According to a first aspect of the present invention there is provided a device for use in the application of force to the cricoid cartilage of a patient undergoing tracheal intubation, the device including means for transmitting force applied to the device to the cricoid cartilage and means for monitoring the force applied.
According to a second aspect of the present invention there is provided a device for use in training an operative in the reproduction of a desired force intended to be applied by the person so trained to the cricoid cartilage of a patient undergoing tracheal intubation, the device including means for transmitting force applied to the device to a patient substitute and means for monitoring the force applied.
According to a third aspect of the present invention there is provided a kit of parts for use in both the training of an operative in the application of force to the cricoid cartilage of a patient undergoing tracheal intubation and in the actual application of said force to such a patient, is the kit comprising a device having means for transmitting force applied to the device to a patient or a patient substitute and means for monitoring the force applied, together with an intermediate component for connecting between the device and the cricoid cartilage of a patient.
Preferably, the device comprises a first part which may be placed directly, or indirectly by means of an intermediate component, on the cricoid cartilage, and a second part coupled to said first part whereby force applied to the second part is transmitted to the first part.
Conveniently, the second part includes a cylinder and the first part includes a piston disposed within the cylinder for movement relative thereto into and out of one end of the cylinder.
Preferably, a seal is provided between the piston and the other end of the cylinder.
Preferably, the means for monitoring the force applied comprises means for monitoring the degree of compression of the space within the cylinder above the piston against a resistive force.
The resistive force may be supplied by a spring disposed between the first part and the second part.
Preferably, the spring is calibrated to indicate the force applied to the device.
Alternatively, the resistive force may be supplied by a pressure gauge in communication with the space within the cylinder above the piston.
For convenience of use, the device preferably includes extension means on which one or more fingers may be placed to apply force manually to the device. For example, the extension means may comprise one or more wings.
The device may be used as it is for the purpose of training an operative in the use of the ACF procedure, by placing the tip (distal end) of the piston on a hard surface or on a manikin, but in order that the same device may be used in the actual application of ACF to a patient, an intermediate component in the form of a U-shaped cricoid yoke is provided between the first part and the patient""s cricoid cartilage.
This yoke, which is preferably moulded from rubber or foam, is conveniently fixed onto the distal end of the piston, to convert the device from a training device into a device for using the ACF procedure on a patient.
According to a fourth aspect of the present invention there is provided a method of applying a desired force to the cricoid cartilage of a patient undergoing tracheal intubation, the method including using on said patient a device having means for transmitting force applied to the device to the patient, and monitoring the force applied.
According to a fifth aspect of the present invention there is provided a method of training an operative in the technique of applied cricoid force (ACF), the method comprising applying force to a patient substitute such as is a hard surface or a manikin using a device having means for monitoring the force applied.